A popular type of slow cooker comprises either a plastic or a ceramic bowl received in a housing, which is commonly made from metal. A lid, usually made from a transparent glass, is removably mounted on the bowl, and has an upwardly protruding knob which can be grasped to lift the lid. The housing has electrically-operated controls and heating means for heating foods placed in the bowl. The housing has handles so that it can conveniently be moved back and forth from a storage shelf and a kitchen counter. Often, a cook may want to move the slow cooker after it is loaded with the food to be cooked from, say, a kitchen counter to a serving table.
The bowls and the lids of slow cookers are not usually made to close tolerances, and the lids are typically not securely engaged with the bowls. This creates a potential for the lid to slide off the bowl when the slow cooker is being carried from one location to another. Also, foods cooked in a slow cooker usually have a significant liquid content which can be spilled if the bowl is tilted while the slow cooker is moved.